Yemeni interrogators suspect the man accused of killing three American missionaries at a Baptist hospital may have ties to Al Qaeda, officials said Tuesday, as U.S. investigators joined the search for those behind the murders.

An FBI team arrived Monday in Jibla, the southern Yemeni town where the killings took place, and worked overnight, an American diplomat said on condition of anonymity. The diplomat would not say whether U.S. investigators were being allowed to directly question the suspect arrested for the slayings, but said the Americans "are very close" to the interrogation.

The U.S. Embassy said it was too early to tell if terrorism was behind Monday's shootings at a Southern Baptist hospital, but Yemeni Prime Minister Abdul-Kader Bajammal included the slayings in a list of terrorist acts he presented to parliament later in the day.

Officials close to the investigation said Yemeni interrogators have strong suspicions the accused gunman has connections to Usama bin Laden's terror network. Yemen is bin Laden's ancestral homeland and has been a fertile recruiting ground for him.

In the attack, the gunman slipped past security at Jibla Baptist Hospital, 125 miles south of the capital San'a, cradling his hidden gun like a baby. He entered a room where the director was conducting a meeting and opened fire at about 8:15 a.m. Monday, officials and witnesses said.

After shooting three people in the head, killing them instantly, the gunman headed to the pharmacy and shot the pharmacist in the abdomen. Yemeni authorities arrested a Yemeni suspect they identified as 30-year-old Abed Abdul Razak Kamel.

The International Mission Board of the Southern Baptist Convention identified the dead as purchasing agent Kathleen A. Gariety, 53, of Wauwatosa, Wis.; Dr. Martha C. Myers, 57, of Montgomery, Ala., and hospital director William E. Koehn, 60, of Arlington, Texas.

Pharmacist Donald W. Caswell, 49, of Levelland, Texas, was hospitalized and was recovering from surgery, his father said.

The 80-bed Jibla hospital, which sits on a hilltop amid trees, treats more than 40,000 patients annually, providing care free to the poor. Hospital officials said the staff included 64 foreigners, including 25 Americans.

President Ali Abdullah Saleh condemned the shootings as "criminal and disgraceful" and pledged to punish the perpetrators.

"We are confident that such a criminal act won't affect the friendship and cooperation between our countries ... but instead strengthen our determination to eradicate terrorism," Saba quoted the president as saying in a message to President Bush.

In past investigations, Americans working alongside Yemenis have complained of having limited access to suspects.

In addition to interrogating the suspect, investigators were questioning prisoners picked up in earlier sweeps of suspected Muslim militants to see what they knew about Kamel. The suspects included some believed linked to Al Qaeda and some to a small Yemeni group known as al-Jihad.

Al-Jihad, which attracted many Yemenis who had fought the Soviets in Afghanistan, had chiefly targeted secular figures from once-socialist southern Yemen. It had not been active for several years.

Earlier, officials had said Kamel claimed to have ties to a cell plotting attacks on foreigners and secular-minded politicians.

The official news agency Saba quoted an official as saying the suspect told interrogators that he plotted the attack in collaboration with Ali al-Jarallah. Yemeni officials say al-Jarallah is a Muslim extremist and a member of the fundamentalist Islamic Reform Party who was arrested for shooting dead a senior Yemeni leftist politician on Saturday.

In his report to parliament, Prime Minister Bajammal included the Jibla shootings among 15 "major terrorist acts" in Yemen since 1997. Others included the Oct. 6 suicide bombing of a French oil tanker Limburg off the coast of Yemen and a similar suicide bombing of the USS Cole off Yemen in October, 2000. Both ship attacks were blamed on Al Qaeda, which also is held responsible for last year's Sept. 11 attacks in the United States.

"Terrorist acts, in particular the attack on the USS Cole and the Limburg tanker, resulted in enormous material and moral damage which have tarnished the image of our country and made it appear a fertile land for terrorism and terrorists," the prime minister said.

Yemen has been a key front in the U.S.-led war on terrorism and its government signed on as Washington's partner after the Sept. 11 attacks.

Anti-American sentiments are running high in the Middle East due to perceived U.S. support for Israel and the standoff with Iraq.

About 30,000 U.S. citizens, most of Yemeni origin, live in the Arab country, the U.S. Embassy said. They were repeatedly warned to take security precautions in Yemen, a country where central government authority is weak, guns are plentiful and Muslim militants have found refuge.

Jerry Rankin, president of the Richmond-Va.-based Southern Baptist International Mission Board, told reporters in Richmond there had been threats against his group's missionaries -- though not specifically against the hospital.

The threats "are taken seriously," he said. "It goes with being a Christian missionary now, but also with being an American."