The NBC report seemingly contradicts multiple CBS News reports. Most recently, on May 19, the outlet reported that US intelligence had identified "at least 10 mines" in the strait. Back in March CBS reported that an official said there were at least a dozen, while another one said fewer than a dozen. CBS attributed this information to officials who weren't named.
https://www.zerohedge.com/geopolitical/us-military-hasnt-identified-single-confirmed-mine-strait-hormuz-officials-tell-nbc