Adam Nossiter / New York Times News Service

BAMAKO, Mali — Algerian officials said Sunday that security forces combing the scene of a bloody four-day hostage siege had discovered many more corpses, some badly burned, at a gas-production complex deep in the Sahara.

They also said for the first time that some of the hostage-takers were captured alive.

“There are a good twenty bodies,” a senior Algerian official said of the grim discoveries at the site on Sunday, a day after a final assault ended the siege. “These must be identified.”

Once they are, the preliminary count of 23 dead hostages seemed certain to rise, officials acknowledged.

“I’m very afraid that the numbers are going to go up,” the Algerian communications minister, Mohamed Said, told France 24 Television.

The standoff between several dozen radical Islamists and Algerian security services came to a bloody conclusion on Saturday when the Algerians assaulted the kidnappers’ last redoubt at the facility, where hundreds of Algerian and scores of expatriate workers were employed.

The victims — from the United States, Britain, France, Japan and other countries — were killed after hours of harrowing captivity in which some were forced to wear explosives.

An unknown number of the hostages died in the assault on Saturday; Algerian officials said they also killed most of the remaining hostage-takers, who they said were followers of Moktar Belmoktar, an al-Qaida-linked warlord based in northern Mali. A regional website reported that he had issued a video claiming responsibility for the attack.

Specifics on exactly who was held hostage, who escaped and who was killed remained patchy and contradictory on Sunday, including the number and status of Americans. One senior U.S. official said that all of the American hostages who were seized at the remote gas field had died, including one identified as dead by the State Department on Friday and as many as nine others.

But another U.S. official said that some of the Americans survived. An official with BP, one of the companies operating the complex, identified one surviving American, and the office of a Texas congressman said there was another. A senior Algerian official interviewed Sunday declared that “seven Americans were liberated.”

Siege aftermath

At least 81 people have been reported dead, including 32 Islamist militants, after a bloody, four-day hostage situation at Algeria’s remote Ain Amenas natural gas plant. Nearly two dozen foreign workers remained unaccounted for late Sunday.

Here’s the latest information from Algeria on the dead and missing:

The dead

• 32 Islamist militants, according to the Algerian government.

• 23 hostages, according to Algeria. Confirmed dead so far include three from Britain, two from the Philippines, one each from the U.S., Romania and France.

• 25 more bodies found Sunday, unclear yet whether they were hostages or militants, according to an Algerian security official.

• One Romanian hostage who had been evacuated died of his wounds, according to the Romanian government.

The missing hostages

• Japan: 10 Japanese working at the plant are unaccounted for, according to their employer JGC Corp.

• Norway: Five Norwegian employees of Statoil are still missing, the energy company said Sunday.

• Britain: Three other Britons still missing and feared dead, the U.K. government said Sunday.

• United States: One Texan is dead, the U.S. has confirmed. A U.S. official said some American hostages escaped or were unaccounted for but would not give any numbers. The militants at first said they had seven American hostages, then later offered to trade two of them for two terrorists behind bars in the U.S., an offer rejected by Washington.

• Malaysia: Two Malaysians are missing, the government says.

— The Associated Press