The two dams outside the city of Derna broke up on September 11 after they were overwhelmed by Storm Daniel, which caused heavy rain across eastern Libya.
The failure of the structures inundated as much as a quarter of the city, officials have said, destroying entire neighbourhoods and sweeping people out to sea.
Government officials and aid agencies have given estimated death tolls ranging from more than 4,000 to over 11,000. The bodies of many of the people killed are still under rubble or in the Mediterranean.
The UN Office for the Coordination of Humanitarian Affairs says at least 9,000 people are still missing.
A statement by the office of General Prosecutor al-Sidiq al Sour said prosecutors on Sunday questioned seven former and current officials with the Water Resources Authority and the Dams Management Authority over allegations that mismanagement, negligence and mistakes contributed to the disaster.
Derna Mayor Abdel Moneim al Ghaithi, who was sacked after the disaster, was also questioned, the statement said.
Prosecutors ordered the eight to be jailed pending the investigation, the statement added.