JAKARTA -- Indonesia has engaged five navy vessels and a maritime surveillance plane to join in search efforts for a missing Malaysian passenger jet carrying 239 people, a senior Indonesian navy officer said here on Sunday.

The joining of Indonesia in the searching efforts was a response to Malaysia's request on Saturday night, Indonesian Navy Spokesperson Untung Suropati said.

"Yes, we sent five vessels that consisted of corvettes and speed patrol boats and also a maritime patrol plane," Untung said as quoted by local media the vivanews.com.

Indonesian becomes the sixth country to dispatch forces after China, Malaysia, Singapore, Vietnam, the Philippines and the United States to search for the missing plane.

Untung said that those Indonesian vessels and plane were embarked on Sunday morning.

"I had been told that our vessels have crossed the northern Malacca Strait boundary lines sometime between 10 and 11 a.m. this morning," Untung added.

He said that the Indonesian navy vessels would focus their efforts in Malacca Strait and Penang.

Untung expressed confusion on the absence of any emergency transmitter signal that should have been issued by the missing plane should it make an emergency landing. He added that as a modern plane Boeing 777-200 must have been equipped with such an instrument.

The Boeing 777-200 aircraft operated by Malaysia Airlines left Kuala Lumpur International Airport for Beijing at 12:41 a.m. Saturday. Contact with the plane along with its radar signal was lost at 1:20 a.m. Saturday when it was flying over the Ho Chi Minh air traffic control area in Vietnam.

The aircraft was carrying 12 Malaysian flight crew and 227 passengers including 154 Chinese. Seven of the passengers were Indonesians.

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