Soldiers joined emergency rescue teams to search for people feared trapped under debris after an explosion in Mexico City.
The blast in a neighbouring building hit the headquarters of state-owned oil giant Pemex, killing at least 25 people and injuring more than 100.
Interior Minister Miguel Angel Osorio Chong told Reuters that the number of casualties is expected to rise.
He said at least one person had been pulled out alive.
A paramedic at the scene told Reuters that as many as 100 people could be trapped.
The blast happened shortly before many workers were due to end their shifts at Pemex, making the area particularly busy.
More top news
Two students and their climbing instructor are feared dead after an avalanche hit a school party in Japan.
The US has strongly condemned Russia's treatment of protesters after the largest anti-government protests in years swept the country.
Prosecutors in South Korea are seeking a warrant to arrest former president Park Geun-hye on corruption allegations.