A Philippines rebel group has denied kidnapping two Americans and a Filipino from a holiday resort on Tuesday.
The separatist Moro Islamic Liberation Front (MILF) told local media that its members were helping the authorities search for the abductees.
Police had earlier said rogue fighters from the group might have been responsible for the kidnapping.
The authorities now believe the more violent Islamist group Abu Sayyaf may have carried out the abduction.
Abu Sayyaf, which is believed to have about 400 fighters in its ranks, has carried out kidnappings of foreigners in the past - usually for ransom.
Its members have fought alongside MILF, but MILF has a ceasefire agreement with the government and has sought to distance itself from Abu Sayyaf.
MILF spokesman Von Al Haq said his group was helping government troops to find the abductees.
"Our ceasefire committee members are working with government counterparts and will share the information we will get from the field," he said in a statement quoted by the Philippines Star newspaper.
On Tuesday a gang of gunmen snatched 41-year-old Gerfa Yeatts Lunsmann, her son Kevin, 14, and nephew Romnick Jakaria, 19, from a resort on the island of Tictabon.
Ms Lunsmann, who was born in the Philippines but is now based in Virginia, was reportedly on holiday visiting relatives.
Philippines government officials said they had not yet heard anything from the armed gang.