CAIRO, Egypt (AP) _ Five men, including three Americans, have been imprisoned for three weeks on suspicion of proselytizing to convert Muslims to Christianity, the American company that employs them said Sunday.

Industrial Systems and Components, an export management firm based in Warrenton, Va., said the suspicions were unfounded and accused Egyptian authorities of mistreating the men.

Mohsen Mabrouk, an assistant to the prosecutor in charge of the case, confirmed the five were being held for interrogation and that no charges had been filed. He refused to say why they were arrested.

The U.S. Embassy refused to discuss the case but said it was in touch with Egyptian authorities and that U.S. diplomats had visited the detained men.

Randy Hoffman, a senior employee at the company's Cairo office, identified the Americans as Robert M. Cunningham of Massachusetts, Brian K. Eckheart of Iowa and Richard P. Dugan Jr. of Indiana. Hoffman said he did not know the men's hometowns.

Cunningham and Eckheart are the top executives in the company's Cairo office, which represents businesses that export computers, machines and other wares.

Hoffman said the others being held are Thomas A. Martin of New Zealand and Abdel-Hamid Adel-Nefa, an Egyptian.

Industrial Systems and Components said in a statement that the men were arrested at their homes on Feb. 21 and Feb. 22 and were being held on suspicion of ''exploiting religion to debase Islam and foment sectarian sedition.''

They are also accused of trying to convert Muslims to Christianity, undermining national security by spreading tension between Christians and Muslims and ''using religion to spread extremist thoughts to denigrate Islam,'' the company said.

Although Egypt's constitution guarantees freedom of religion, it is illegal to promote any religion other than Islam.

Mark Grant, the company's president, was quoted in the statement as saying: ''There has been no sedition by anyone associated with our company. Rather than debasing Islam, our employees are specifically instructed to observe traditions of Islam ... so as not to offend the Egyptians.''

Hoffman said Nefa is a Muslim and described the others as ''followers of Jesus Christ'' but denied any of them had tried to convert Muslims to Christianity.

Hoffman said some of the men were mistreated during their arrests and detentions.

''When they went to arrest Martin, they aimed guns at his children,'' he said in a telephone interview. ''At Cunningham's home, they cut telephone lines. They ransacked the homes.''

The detainees have complained that they were forced to squat for 10 hours and were threatened with beatings. Martin and Nefa were blindfolded at one point, Hoffman said.