An engineering firm hired to oversee the reconstruction of city buildings and infrastructure damaged by Hurricane Katrina has been overcharging the city, including billing for theater tickets and a flight to Las Vegas, an internal investigation found.

The report by New Orleans Inspector General E.R. Quatrevaux said the flawed contract with MWH Americas Inc. has hurt the city’s recovery, placing blame on both the company and city officials. The city’s slow rebuilding process continues to anger residents, and the uneven recovery was a major issue in the campaign leading up to last month’s mayoral election.

Quatrevaux advised scrapping the deal with the Broomfield, Colo.-based firm in the report, first made public Thursday by The Times-Picayune. The company’s work previously had not garnered much criticism.