(Adds information from second filing) HOUSTON (Dow Jones)--A fluid catalytic cracking unit hit a snag early Wednesday at BP PLC's (BP, BP.LN) Texas City, Texas refinery, according to a filing with environmental regulators. The cause is unknown, the filing with the Texas Commission on Environmental Quality said. The Texas City refinery can process up to 455,000 barrels of crude a day. Later on Wednesday, BP made a second filing with regulators that said the unit "will resume full operations after responding to a unit upset." The filing didn't say when the unit would restart but did say that it expected any emissions from the event to cease by 1 a.m. CT Thursday. -By Susan Daker, Dow Jones Newswires; 713-547-9208; susan.daker@dowjones.com (END) Dow Jones Newswires July 07, 2010 17:38 ET (21:38 GMT)