(CNN) -- At least 27 people were killed and 52 injured after an oil pipeline exploded Sunday morning in central Mexico, the state-run news agency said.
The cause of the explosion in San Martin Texmelucan, in Puebla state, was under investigation, but preliminary reports pointed to the illegal extraction of oil from the pipe, said Laura Gurza, coordinator for civil protection in Puebla.
The situation was under control, but the extent of the damage was still being assessed, Civil Protection Director Miguel Angel Martinez said. The pipe belongs to Pemex, the state-owned oil monopoly.
Some 32 houses were lost in the blast, and 80 others were partially damaged, Martinez said.
Video from the scene showed a huge billowing wall of smoke that reached into the sky. Rescue workers could be seen walking through the still-smoldering streets.
Twelve of the people killed in the blast were children, the state news agency Notimex reported, citing Gurza.
About 5,000 nearby residents were evacuated, officials said, and some 200 were in a government shelter.
Oil theft has been a persistent problem for Pemex, and has been on the rise since President Felipe Calderon took office. A Washington Post investigation found that drug cartels were increasingly diversifying into other areas, including oil theft, to the tune of more than $1 billion in a two-year period.
CNN en Espanol's Krupskaia Alis and Rene Hernandez contributed to this report.