© Reuters. Flood waters caused by Tropical Storm Harvey encompass the Motiva Enterprises LLC in Port Arthur, Texas

HOUSTON (Reuters) - The largest U.S. refinery was restarting production on Monday for the first time since being shut nearly two weeks ago by Hurricane Harvey, said sources familiar with plant operations.

Motiva Enterprises [MOTIV.UL] restored the 325,000 barrel per day (bpd) VPS-5 crude distillation unit at its 603,000 bpd Port Arthur, Texas, refinery to minimum production levels early in the day, the sources said.

After bringing the VPS-5 online, Motiva began restarting the 105,000-bpd Hydrocracking Unit 2, the sources said. The HCU-2 is a lucrative source of motor fuel exports for Motiva.

Motiva did not immediately reply to requests for comment about operations at the refinery, which has been shut since Aug. 30 due to flooding from Harvey.

Last Thursday, the VPS-5, HCU-2 and the 110,000 bpd coking unit were ready to resume production after being placed on circulation in which the units were at operating temperatures and circulating feedstock, the sources said.

However, Motiva had been waiting for adequate crude supply to be restored to the VPS-5 before restarting production, according to the sources.

Motiva said last week the Port Arthur refinery would resume production at 40 percent capacity by Monday. Motiva did not give a timeline for fully restoring output.

Sources have said it will take four to eight weeks to return the full refinery's production.

CDUs do the initial refining of and provide feedstock for all other units.

Hydrocrackers use hydrogen to produce motor fuels, especially diesel, from gas oil. Cokers produce motor fuel feedstocks and convert residual crude to petroleum coke, a coal substitute.