MIAMI (AP) _ Five missing Contra officials said in a letter written before their disappearance that they would hold the rebels' military chief responsible for any attack on them, a family member said Thursday.

Some of the five men had accused Contra leader Col. Enrique Bermudez of corruption and had charged that he surrounded himself with supporters of deposed Nicaraguan dictator Anastasio Somoza Debayle.

The five were rounded up at their hotel in Honduras on Tuesday by Honduran security police, said Marsha Lacayo, wife of missing Contra military adviser Donald Lacayo.

The men, some of whom spoke to their wives at the Honduran security police headquarters after their arrest, said they expected to be expelled from the country Thursday. But they failed to show up at the airport in the Honduran capital of Tegucigalpa and their whereabouts are unknown, Mrs. Lacayo said in Miami on Thursday night.

The men had written a letter on April 16 blaming Bermudez in advance for ''any attack on our lives, damages, injuries or deaths,'' said Mrs. Lacayo.

The letter was to be opened in case anything happened to any of the signees, she said.

''There is no doubt that Bermudez is responsible,'' said Mrs. Lacayo.

At a news conference in Washington on Thursday morning, Bermudez denied having any information about the whereabouts of the missing Contras.

Bermudez, a former colonel of Somoza's hated National Guard, has been at the center of a bitter power struggle within Contra ranks for several weeks.

Adolfo Calero, one of the five directors of the Nicaraguan Resistance, a Contra umbrella group, reportedly agreed with the dissidents that Bermudez should be removed, in part because he has opposed parts of the peace agreement with the leftist Sandinista goverment.

Calero tried to persuade the four other directors to remove Bermudez, but the leaders deadlocked.

One of the five men detained is Enrique Sanchez, brother of Contra director Aristides Sanchez, according to Mrs. Lacayo. Enrique Sanchez, like Lacayo, was a civilian aide to the Contra military forces.

The other detainees were Walter Calderon Lopez, known as Commander Tono, Tirzo Ramon Moreno, known as Commander Rigoberto, Alejandro Montealegre, and a rebel pilot identified only as Waikita.

One commander, Diogenes Hernandez Membreno, also known as Fernando, escaped detention when the others were arrested and is in hiding, Mrs. Lacayo said. Until January, Fernando was Bermudez's personnel assistant.