A handful of oil tankers were racing toward the Strait of Hormuz on Friday after Iran declared it open, even as industry groups urged caution and several shipowners and traders said they needed more clarity about the status of the waterway before making any decisions.

A Pakistan-flagged tanker that entered the Persian Gulf over the weekend has become the first carrier to exit through the Strait of Hormuz with a crude cargo since a US blockade began on Monday, underscoring just how limited traffic through the vital chokepoint remains.