U.S. President Barack Obama on Friday ordered investigation into an oil rig explosion that led to a massive oil spill in the Gulf of Mexico, threatening fragile coastal environment there.

Obama said he had asked Interior Secretary Ken Salazar to conduct "a thorough review of this incident" and present a report in 30 days on measures to be taken to prevent another incident.

The oil rig is the Deepwater Horizon rig off the Louisiana coast. An explosion occurred in the rig last Tuesday, and 11 workers were missing. The rig sank after burning for 36 hours, and officials found oil was leaking Saturday. Coast Guard said oil was leaking at a rate of 5,000 barrels a day.

The leak soon formed a giant slick, and oil began washing onto Louisiana shores Friday. Also on Friday, a small mobile inland drilling unit overturned in a Louisiana canal. The Coast Guard is responding to the incident.

Faced with environment disaster, Louisiana and the federal government joined hands in trying to contain the spill. So far success has been elusive. Salazar, Homeland Security Secretary Janet Napolitano and Environmental Protection Agency head Lisa Jackson flew down to Louisiana to survey the slick and containment efforts.

Obama said the government has dispatched about 1,900 federal response personnel with 300 boats and aircraft to help the containment effort.

The states of Louisiana, Florid and Alabama have declared state of emergency because of the spill.