Jacobs won the world indoor title last March

The US Olympic Committee confirmed the steroid was detected in a sample given by Jacobs at last June's US national championships.

USOC also announced that 400m runner Calvin Harrison had tested positive for the stimulant modafinil.

Both athletes are disputing their cases, USOC said.

Reports that Jacobs had failed a drugs test first surfaced in October.

She raised eyebrows when she broke the 13-year-old world indoor 1500m record at the age of 39 earlier in the year.

Jacobs was the first woman to run under four minutes for the 1500m indoors.

American athletes failing drugs tests now face possible lifetime bans and $100,000 fines as a result of a new zero tolerance initiative introduced by United States Track and Field.