ISTANBUL (AP) -- Eighteen people, including company executives, have been detained as Turkish officials investigate the mining disaster that killed 301 people, a domestic news agency reported Sunday.

The Dogan news agency said Ramazan Dogru, general manager of the mine owned by Soma Holding, and its operations manager, Akin Celik, were among those detained. It said prosecutors were questioning five people Sunday but did specify whom.

Government and company officials have insisted that the mine was inspected regularly and negligence was not a factor. But reacting to widespread public anger, government officials promised to investigate and pledged that any mine officials found to be negligent would be prosecuted.

The Milliyet newspaper said Saturday that a preliminary report by a mine safety expert who inspected the Soma mine suggested that smoldering coal caused the mine's roof to collapse. The report said the tunnel's support beams were made of wood, not metal, and the mine had too few carbon monoxide sensors.

Company officials have described safety standards as high, noting that the mine contained 50 gas sensors and employees were provided gas masks.

At a press conference Friday, Celik said thick smoke from the underground fire killed many miners who were not carrying gas masks. Rescue workers entering the mine complained of high levels of carbon dioxide and carbon monoxide.

On Saturday, rescue workers retrieved the bodies of the last two miners missing in the disaster, putting the death toll at 301, Energy Minister Taner Yildiz said.