MEXICO CITY – State-owned oil giant Petroleos Mexicanos (Pemex) said its Mexico City headquarters was evacuated on Monday after a bomb threat was received, but no explosives were found.

“A bomb threat was received at Pemex Tower, under the security protocol an evacuation was carried out so the corresponding inspection” could be conducted, Pemex said in a Twitter post.

After the building was searched, officials determined it was “a false alarm” and “we are getting back to work,” Pemex CEO Jose Antonio Gonzalez said.

About 6,000 people work at the Pemex office complex in the Veronica Anzures district, a Pemex representative told EFE.

On Jan. 31, 2013, an explosion caused by a gas leak killed 37 people and injured more than 100 others at Pemex headquarters.

The explosion was caused by an accumulation of methane gas ignited by a spark, officials said.

Workers were doing maintenance on the structure’s support columns when the blast happened.

The main tower of the office complex, a 56-story structure, was not damaged in the explosion.