(Adds fire expected to be exinguished by Thursday, updates number of wounded)
By Ana Isabel Martinez
MEXICO CITY, July 23 (Reuters) - Mexican state oil company Pemex said on Wednesday that work at most of its Ciudad Madero refinery in northern Mexico had been halted while it tries to contain an ongoing blaze in a storage tank.
Pemex said in a statement that the fire would likely be extinguished by midday on Thursday as the company's emergency personnel and firefighters from nearby cities worked together, the company said in a statement.
"Most of the refinery plants are stopped for security," a Pemex spokesman said earlier in a telephone interview, adding that there was a very low risk of the fire spreading to other parts of the refinery, located in Tamaulipas state.
Local television images showed out-of-control flames at the site, where the blaze began during the night in a gasoline storage tank.
Pemex said two workers suffered light burns and 21 others were treated for dehydration and exhaustion after battling the blaze. Around 200 people who live near the refinery had been evacuated, the company said.
The Ciudad Madero refinery is the smallest of Pemex's six domestic refineries, with a total crude processing capacity of 190,000 barrels per day. (Additional reporting by Simon Gardner and Veronica Gomez; Editing by Paul Simao and Lisa Shumaker)