LONDON (AP) ― Britain’s Olympic security plans fell under fresh scrutiny Sunday, with a newspaper reporting that several people on a terror watch list have been waved through airport border controls without being flagged and officials trying to calm the uproar over a security contractor’s failure to provide its promised number of staff.

The Observer newspaper’s report is the latest in a series of last-minute concerns to surface as London gets ready to host the Olympic Games from July 27 to Aug. 12.

The paper said that, since the start of the month, immigration staff at London’s Heathrow Airport had missed several people on a security watch list whose arrival in the country was meant to have been reported to counter-terrorism police or Britain’s domestic intelligence service.

The newspaper cited unions as suggesting that staff brought in to help relieve the pressure at Heathrow, which has faced recurring problems handling large influxes of passengers, weren’t being properly trained.

The airport, Europe’s busiest, has recently struggled to clear huge lines that build up at immigration checkpoints during peak times, leading to fears of Olympics-related chaos as tourists fly in to watch the games.

The report left it unclear whether the people on the watch list were still in the country, whether they were intercepted later, or exactly why they had attracted the attention of counter-terrorism officials in the first place. Britain’s Home Office declined to comment Sunday on the Observer story.

British authorities already are under pressure over the failure of security contractor G4S to deliver some 10,400 personnel to protect stadiums and other events. The blunder has forced the government to call in an extra 3,500 troops to guard the games ― that’s over and above the 7,500 troops already promised to help out at some 100 venues and sensitive sites.

The Independent on Sunday newspaper reported that top Home Office officials had been warned by police nearly a year ago about concerns over the ability of G4S to provide enough staff for the Olympic Games, while the BBC quoted the chief of Britain’s National Association of Retired Police Officers as saying that his group could have helped fill the shortfall in manpower ― if only G4S had bothered getting in touch.

“With enough notice we could have provided a significant number (of retired officers),” he told the BBC. “They have made no effort to do that.”

The British minister in charge of the Olympics appeared on a talk show Sunday to try to contain the scandal ― noting that G4S boss Nick Buckles had apologized and would be footing the bill for the last-minute military deployment ― as well as up to $31 million for failing to live up to his company’s end of the deal.