German prosecutors say they have searched a yacht that may have been used in the sabotage of the Nord Stream gas pipelines from Russia to Germany. But they were unable to confirm U.S. intelligence claims that a pro-Ukrainian group was responsible for blasts last September that cut off the main supply of Russian gas to Western Europe. The German prosecutor’s office said in a statement that a yacht had been searched this January “in connection with a suspicious ship rental” but had revealed no reliable conclusions. German reports say a group of five men and women, all using forged passports, rented the Ukrainian-owned yacht from a company based in Poland. Separately, German Defense Minister Boris Pistorius suggested the attack could have been a “false flag” operation to smear Ukraine. “We have to make a clear distinction whether it was a Ukrainian group, whether it may have happened at Ukrainian orders, or a pro-Ukrainian group [acting] without knowledge of the government. But I am warning against jumping to conclusions,” he said.