JERUSALEM — Expensive cigars for him and pink Champagne for her?

On Thursday evening, for the second time this week, investigators grilled Prime Minister Benjamin Netanyahu of Israel at his official residence as a suspect in an investigation into possible corruption, the details of which have largely been kept under wraps.

The police said in a brief statement that Thursday’s session had lasted five hours and that Mr. Netanyahu had been questioned under caution on suspicion of receiving improper gifts and favors. He was also interviewed about a separate case, the police said, without offering any details.

Even as the questioning was underway, Israel’s news media were reporting about some gifts that had led to suspicions of graft.

A Hollywood producer and longtime friend of Mr. Netanyahu’s is said to have supplied him with boxes of cigars for years, the Haaretz newspaper and Israel’s Channel 2 News reported. The news channel added that the American-Israeli producer, Arnon Milchan, had brought Mr. Netanyahu’s wife, Sara, bottles of fine Champagne.