Mexican state oil giant Pemex says the death toll from a petrochemical plant blast in the southeastern oil hub of Coatzacoalcos has risen to 28.
In a statement, Pemex said it had identified 25 bodies and that three more were still unidentified.
It added that 18 people remained hospitalised.
Pemex has said the accident was caused by a leak, but has not fully explained what happened.
The oil firm said it would continue to scour the blast site, but that progress was slow, given the scale of the damage.
The massive explosion took place on Wednesday afternoon (local time) at the facility's chlorinate 3 plant in the Gulf state of Veracruz, sending a black cloud of smoke hundreds of metres into the air and giving off a powerful smell of ammonia.
The blast occurred at a vinyl petrochemical plant that is a joint venture between Pemex's petrochemical unit and majority owner Mexican plastic pipe maker Mexichem.