WASHINGTON — The FBI spied on the Branch Davidian sect during the 51-day siege at Waco with an array of sophisticated gadgets, including eavesdropping devices that were slipped into the compound with supplies.

Law enforcement sources said radio transmitters smaller than cigarettes were smuggled into David Koresh's Mount Carmel cult headquarters, while heat-sensitive surveillance equipment "watched" the compound from outside.

In Waco yesterday, FBI agent Jeff Jamar declined to say whether the FBI had used listening devices planted inside the compound before Monday's fatal attempt to force the cult members to give up.

"I won't discuss what our intelligence techniques are," Mr. Jamar said. "I'll just say to you that we had outstanding intelligence in many respects, but very inconsistent and sometimes very inconclusive."

The Associated Press, quoting unidentified officials, said the FBI poured tear gas into the cult compound in Waco only after authorities learned through a listening device that David Koresh was becoming more violent.

Sources in separate federal law enforcement agencies, speaking on condition they not be identified, confirmed to Cox Newspapers that the FBI had managed to plant tiny electronic listening devices inside the compound.

The sources indicated that eavesdropping devices went in with food and supplies that periodically were provided by federal agents to Mr. Koresh and his followers. The sources declined to say how the devices were concealed.

In recent days, shipments of milk, magazines, typewriter ribbons and writing supplies had been given to those holed up in the compound.

Earlier, the cult members were provided with a video camera and video tape, which they used to take pictures of the children in an effort to convince federal agents that the youngsters in the compound were being well treated and were not in poor health.

Sources said the eavesdropping bugs -- in the surveillance business they sometimes are referred to as "quick drop" devices -- have miniature batteries and microphones. The batteries provide enough power to transmit eavesdropped conversations for up to 24 hours, in some cases.

The sources also said that infrared equipment, which ascertains images from body heat, was used in an attempt to detect the presence of cult members in various parts of the compound.

In defending the FBI's attempt to force an end to the standoff, Attorney General Janet Reno said Monday that federal authorities believed that child abuse was occurring in the cult's compound. She did not say how they learned of the alleged abuse.

One source said agents used "Flirs," or forward looking infrared systems, to watch outdoor areas of the compound at night and even determine whether specific rooms were occupied.

Read the Tribune-Herald's 7-part investigative series on the inner workings of the Branch Davidians. Hours after Part Two appeared in print, the ATF raided the group's compound.

Read the Tribune-Herald’s account of the ATF raid on the Branch Davidian compound on Feb. 28, 1993. Four ATF agents and six in the compound were killed in the gunfight.

Read the daily news accounts of the 51-day siege at the Branch Davidian compound near Elk, which began Feb. 28 and lasted until April.

Read the accounts of April 19 and beyond: FBI agents began inserting canisters of tear gas into the Branch Davidian compound in the early morning hours. By noon, it was on fire.