A powerful earthquake that measured 6.4 magnitude hit Mexico on Thursday. It was so strong that it sent office workers scrambling outside of their buildings and destroyed a bridge in the south.

The quake's epicentre was recorded in the western Mexican state of Guerrero, about 15 km north of Tecpan de Galeana, according to data released by the U.S. Geological Survey. It had a depth of 14.9 miles just inland from the Pacific Coast. No tsunami alert was triggered.

The Pacific Tsunami Warning Center did not issue a tsunami alert, saying initial indications point no threat to Hawaii.

It was the second big quake the country's region experienced in a month's time. The last was on April 18 when a 7.2 magnitude quake hit the same state. There were likewise no reports of major damage that time.

Thursday's quake, according to USGS, was an aftershock of the April 18 temblor.

"The earthquake is indeed within the Guerrero Seismic Gap," William Barnhart, USGS research geophysicist, told AP. "But since it is consistent with being an aftershock of the magnitude-7.2, it is neither an abnormal event, nor does it significantly reduce the remaining stored stress in the seismic gap."

It is also very much possible the Guerrero Gap will produce a quake as strong as magnitude 8.4. Only that it is not known when this would happen.

Thursday's temblor was so strong people everywhere panicked. It was even felt 277 km away in Mexico City.

"At first it felt like a jolt and then it started to move. We are used to it but you never know how long it will last or how strong it will be, which is why we always evacuate," Daniel Rodriguez told AFP. An engineer, he fled his second-floor Mexico City office.

"It was very scary. Some of my colleagues suffered panic attacks because the buildings moved," Carmen Lira, a secretary in Mexico City, told the Los Angeles Times. "It felt very strong."

Even Finance Minister Luis Videgaray, who was then delivering a speech at the National Palace in Mexico City when the quake struck, called for a recess.

"If it's alright with you, we will take a break because it is shaking," Mr Videgaray calmly told the audience.

Trading activity at Mexico's stock exchange was suspended from 12:24 p.m. to to 12.53 p.m. Mexico City time, following the earthquake.

Crisoforo Otero Heredia, mayor of Tecpan, said the quake caused some roofs to cave in. But there were no injuries.

In Chilpancingo, the capital of Guerrero state, a wall had collapsed.

Large sections of Mexico City were devastated in 1985 when a magnitude-8.1 quake struck, killing 9,500 people.

Patients sit together outside a hospital after they were evacuated following an earthquake in Acapulco, in Guerrero state, April 18, 2014. The powerful earthquake struck Mexico on Friday, shaking buildings in the capital and sending people running out int
Patients sit together outside a hospital after they were evacuated following an earthquake in Acapulco, in Guerrero state, April 18, 2014. The powerful earthquake struck Mexico on Friday, shaking buildings in the capital and sending people running out into the street, although there were no early reports of major damage. The magnitude 7.2 quake was centered in the southwestern state of Guerrero, close to the Pacific beach resort of Acapulco, the U.S. Geological Survey (USGS) said. Reuters/Jesus Solano
People stand on a street after evacuating a building following an earthquake in Mexico City April 18, 2014.
People stand on a street after evacuating a building following an earthquake in Mexico City April 18, 2014. The magnitude 7.2 quake was centred in the south-western state of Guerrero, close to the Pacific beach resort of Acapulco, the U.S. Geological Survey (USGS) said. Some residents of the capital ran outdoors in their pajamas after the quake. Electricity was cut off in parts of the city and some residents said paintings fell off the walls while small parts of masonry crumbled inside apartment buildings. REUTERS/Bernardo Montoya Reuters
A man inspects the damage in his apartment following an earthquake in Mexico City April 18, 2014. The magnitude 7.2 quake was centred in the south-western state of Guerrero, close to the Pacific beach resort of Acapulco, the U.S. Geological Survey USGS
A man inspects the damage in his apartment following an earthquake in Mexico City April 18, 2014. The magnitude 7.2 quake was centred in the south-western state of Guerrero, close to the Pacific beach resort of Acapulco, the U.S. Geological Survey (USGS) said. Some residents of the capital ran outdoors in their pajamas after the quake. Electricity was cut off in parts of the city and some residents said paintings fell off the walls while small parts of masonry crumbled inside apartment buildings. REUTERS/Bernardo Montoya REUTERS/Bernardo Montoya
A pregnant woman has her blood pressure measured by a hospital staff
A pregnant woman has her blood pressure measured by a paramedic after she and colleagues were evacuated following an earthquake in Mexico City April 18, 2014. The magnitude 7.2 quake was centred in the south-western state of Guerrero, close to the Pacific beach resort of Acapulco, the U.S. Geological Survey (USGS) said. Some residents of the capital ran outdoors in their pajamas after the quake. Electricity was cut off in parts of the city and some residents said paintings fell off the walls while small parts of masonry crumbled inside apartment buildings. REUTERS/Bernardo Montoya REUTERS/Bernardo Montoya
A firefighter works to demolish a damaged wall of a building after a 6.4 magnitude earthquake in Mexico City May 8, 2014. The earthquake shook Mexico City on Thursday, rattling buildings and prompting office evacuations. The U.S. Geological Survey put the
A firefighter works to demolish a damaged wall of a building after a 6.4 magnitude earthquake in Mexico City May 8, 2014. The earthquake shook Mexico City on Thursday, rattling buildings and prompting office evacuations. The U.S. Geological Survey put the quake epicenter in the western Mexican state of Guerrero at a depth of 14.9 miles (23.9 km) just inland from the Pacific Coast. REUTERS/Henry Romero REUTERS/Henry Romero
People walk down the stairs of a building after a 6.8 magnitude earthquake in Mexico City May 8, 2014. A 6.8 magnitude earthquake shook Mexico City on Thursday, rattling buildings and prompting offices to be evacuated, but there were no immediate details
People walk down the stairs of a building after a 6.8 magnitude earthquake in Mexico City May 8, 2014. A 6.8 magnitude earthquake shook Mexico City on Thursday, rattling buildings and prompting offices to be evacuated, but there were no immediate details on any damage.The U.S. Geological Survey put the quake epicenter in the western Mexican state of Guerrero, at a shallow depth of just 6.2 miles. REUTERS/Henry Romero REUTERS/Henry Romero
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