1.   Officials at BASF Mexicana SA, which this year opened a crystal polystyrene plant in Altamira, in Tamaulipas state, were not immediately available for comment.

2.   Chevron Chemical is also considering building a wholly owned polystyrene plant in Shanghai, China.

3.   Production at the polystyrene plant was halted immediately.

4.   Two workers at a BASF polystyrene plant were killed in an explosion Monday, a spokeswoman for the chemical concern said.