Caterpillar Inc. equipment is on display for sale at a retail site in San Diego, California, U.S., March 3, 2017. REUTERS/Mike Blake

WASHINGTON (Reuters) - The U.S. International Trade Commission said on Wednesday it had launched an investigation into allegations that German manufacturers Wirtgen GmbH and Joseph Voegele AG infringe on patents held by Caterpillar Inc CAT.N.

The ITC said its investigation would look into road construction machines, including road milling and road paving machines.