MANILA- A bomb threat last month prompted the MRT-3 to heighten security measures for its half a million daily riders, the Department of Transportation said Friday.

The MRT-3 management received the bomb threat via email last Jan. 3 and immediately coordinated with police, the DOTr said.

"That's one reason kung bakit po kami naghihigpit ng seguridad (That's one reason why we tightened security) following recent attacks in Mindanao. We just wanted to be cautious, since we have thousands of passengers daily," the agency said in a message to reporters.

"We do not want to compromise the safety and security of our passengers and personnel, we will not lax and we will implement a more effective security measures in our trains and stations," it said.

Transport authorities banned all bottled drinks in train stations in late January following twin blasts in Jolo, Sulu, which left 22 people dead and more than 100 hurt.

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-- with a report from Raffy Santos, ABS-CBN News