Sources: Drug test for Keenan Allen

California's Keenan Allen, the No. 1-rated wide receiver on some teams' boards, was red-flagged for a drug test at the scouting combine in Indianapolis and ordered to undergo another test this month, league sources have said.

Allen's agent, J.T. Johnson, denied that his client has failed any drug test. One source said Allen had suspiciously high levels of water in his system.

The results of his most recent test are unknown at this time, but it will be another question that follows Allen as he tries to bounce back from the knee issues that prevented him from working out at Indianapolis.

ESPN.com's Mel Kiper Jr. has Allen ranked fourth among prospective receivers and going 40th overall to the Tennessee Titans in his most recent mock draft.