Federal regulators have subpoenaed recent trading records from several Nymex traders as part of a widening investigation into the sharp rise in oil prices on Monday.

The subpoenas are part of an examination announced by the Commodity Futures Trading Commission on Monday, soon after the price for an expiring futures contract on the Nymex surged in the last hour of trading, according to people briefed on the continuing investigation.

In that announcement, Walter Lukken, the agency’s acting chairman, said investigators were closely monitoring the price move, which came as the financial markets were struggling to recover from the upheaval of the previous week.

Later on Monday, Mr. Lukken was briefed on the episode by Craig Donohue, the chief executive of the CME Group, which owns the Nymex, according to people who were involved in those arrangements.