NAIROBI, Kenya — The FBI is helping Kenyan authorities investigate the cause of a huge blaze that paralyzed Nairobi airport, a police official said Friday.

Investigators have still not established what caused Wednesday's blaze, which raged out of control for several hours.

The airport's arrivals hall was gutted in the fire, which forced east Africa's main hub to close.

"We are not carrying out our investigation alone, we're getting help from our partners including the FBI," a senior police official said on condition of anonymity.

"Other agencies have also expressed their support and promised to join in."

The fire broke out 15 years to the day after the twin bombings by al-Qaida targeting the U.S. embassies in Nairobi and in the Tanzanian economic capital Dar es Salaam that left 224 people dead.

However, there is no indication that the incidents were linked, and the government has urged people not to speculate about the cause of the fire.

Kenya Airways resumed international flights on Thursday and foreign carriers started using the airport on Friday.

"Most companies are operating, even foreign ones," Eric Kiraithe, head of security at JKIA told AFP.