An Air Self-Defense Force C-130 transport will leave for Thailand Thursday to join a U.S. military-led relief operation for survivors of the Dec. 26 tsunamis, the Defense Agency said Wednesday.

The airplane will take relief supplies from the Royal Thai Naval Air Force Base in Utapao, where the U.S. is coordinating its relief efforts, to the northern part of Sumatra Island in Indonesia, the agency said.

If necessary, the agency might send another C-130 to help, it said.

A 20-member advance team of Defense Agency officials and Self-Defense Forces officers departed for Utapao on Tuesday to assess the situation.

"(The team) has reported that there is no problem with operating C-130s and they are much needed," an agency official said.

Depending on the team's findings in Sumatra and other places in the region over the next few days, Japan will dispatch more forces -- most likely medical and helicopter units from the Ground Self-Defense Force and a Maritime Self-Defense Force transport ship, the agency said.

The C-130 and 40 crew members will leave the ASDF base in Komaki, Aichi Prefecture, on Thursday morning, the agency said.

Tally of missing: 236

The whereabouts of 236 Japanese citizens who might have been traveling through areas hit by the Dec. 26 earthquake and tsunamis in the Indian Ocean was still unknown as of Wednesday, a Foreign Ministry spokesman said.

Ministry Press Secretary Hatsuhisa Takashima told reporters that the 236 were believed to have been traveling in Thailand, Sri Lanka and the Maldives.

The number was based on about 3,310 inquiries the ministry received from people who said their relatives and friends might have been in the devastated areas.

The ministry has also been unable to track down another 292 people among the inquiries who were believed to have been traveling outside the devastated areas, ministry officials said.

"We're not sure to what extent" the information on these people is reliable, Takashima said.