(Adds background including why risk of fire, explosion is raised)
Aug 29 (Reuters) - All residents within 1.5 miles (2.4 km) of a chemical plant in southeast Texas were evacuated on Tuesday as a "precautionary measure" because of the rising risk of an explosion, the local fire marshal's office said in a Twitter message.
Earlier on Tuesday, the owner of the plant, Arkema SA , said in a statement the situation at its Crosby, Texas, plant "has become serious" and evacuated all of its staff from the facility.
Crosby is about 25 miles (40 km) northeast of Houston and in the 2010 U.S. census had a population of 2,300 people.
"As a protective measure Harris County has evacuated all residents within 1.5 miles of the Arkema facility," said a Twitter message from the Harris County Fire Marshal Office.
"There is a potential for a chemical reaction leading to a fire at the facility, which could produce a large amount of black smoke," the fire marshal, citing Arkema, said.
"While we do not believe there is any imminent danger, the potential for a chemical reaction leading to a fire and/or explosion within the site confines is real," the company said.
Arkema said the plant has been hit by more than 40 inches (102 cm) of rain, was heavily flooded and without electricity since Sunday. Back-up generators have largely been swamped.
Maintaining refrigeration for chemicals that must be stored at low temperature is key, the company said. After losing generators, workers transferred products from the warehouses into diesel-powered refrigerated containers.
But the floodwaters also compromised the back-up containers, and the company is monitoring temperature levels remotely, it said.
Harvey, which came ashore in Texas last week as a powerful Category 4 hurricane, has caused catastrophic flooding.
The Arkema plant in Crosby produces organic peroxides. It has been closed since Friday but had a skeletal staff of about a dozen in place. Other Texas chemical plants have also shuttered production because of the storm.
Anglo-Swiss chemicals firm Ineos Group Holdings SA said it has been forced to shut Chocolate Bayou Works and Battleground Manufacturing Complex. INEOS Nitriles' Green Lake facility are following hurricane procedures and are temporarily shut down, spokesman Charles Saunders said.
Huntsman Corp said it has closed six chemical plants in Texas, along with its global headquarters and advanced technology center in Texas. (Additonal reporting by Bernie Woodall in Fort Lauderdale, Fla. and Jarret Rensaw in New York; Editing by Lisa Shumaker and Cynthia Osterman)