UNITED NATIONS (AP) _ The United Nations is investigating possible irregularities in the awarding of contracts in major peacekeeping operations, U.N. officials said Thursday.

The announcement of the investigation came a day after U.N. officials announced that eight staff members in New York were suspended without pay, pending a full investigation into the handling of some contracts.

Details relating to the contract investigations and the July 9 suspension of the employees were scarce. But the announcements highlighted management problems in the U.N. bureaucracy at a time when peacekeeping operations are expanding worldwide.

U.N. officials said the suspended employees, who were not identified, were not being disciplined, but were asked to provide written explanations of their conduct.

Joe Sills, spokesman for Secretary-General Boutros Boutros-Ghali, said Thursday only that the U.N. probe involves ''charges of impropriety.'' He would not elaborate.

Separately, he said that all flights in Cambodia involving the Canadian charter company, Skylink Aviation Services, had been resumed.

On Wednesday, U.N. officials said that Skylink had threatened to ground its planes serving in the U.N. peacekeeping force in Cambodia unless it received payment by Thursday. About $20 million was said to be involved.

Sills said there was no connection between the probe into the contract awarding and the Skylink issue.

But U.N. diplomats, speaking on condition of anonymity, said that unsuccessful competitors from the United States and other countries have been complaining about the awarding of contracts in general and Skylink in particular.

Sills told reporters Thursday that the U.N. contracts are awarded through competitive bidding.

Skylink has not been accused of any wrongdoing, and U.N. officials did not explain the arrears in payments.

Skylink transports U.N. troops and equipment for peacekeeping operations in Cambodia, Angola, Iraq, Kuwait, Mozambique, Somalia, Western Sahara and the former Yugoslavia.

Cambodia is the United Nation's largest operation, with a budget of about $1.6 billion. Millions of dollars in contracts have been awarded for the mission, and Skylink has about 40 helicopters there.

Several months ago Dick Thornburgh, the former U.N. undersecretary-general for administration, issued a scathing report about mismanagement, fraud, incompetence and numerous other problems in the vast U.N. system.

His successor, Melissa Wells, an American, also is trying to reform the U.N. management system at a time when the United States, the biggest contributor, wants to ensure that funds are spent efficiently.