The Panama Canal Authority said it will add extra slots allowing ships to pay big premiums to transit the waterway, which has become congested due to an ongoing drought.

The special auctions allow vessels that have been waiting for a long time to pay a one-off fee — at times recently reaching several million dollars — in order to transit the canal. Only vessels that have been waiting for 10 days or more will be eligible to participate, according to an advisory.

The sales of slots to get from one side of the conduit to the other via auction have been increasingly lucrative in recent months, with shipping companies paying a total of about $235 million so far this year to get through. Extremely low levels of rainfall have left the lake that feeds the canal with limited water, in turn forcing the body in charge of the conduit to curb the number of daily transits into next year.

That has left vessels with a handful of options: wait a long time to transit, divert and sail thousands of extra miles around South America, or pay up to access a quicker transit slot.

“Vessels without reservation may experience indefinite delays,” according to the advisory, which noted that the new auctions are designed for ships “that have been waiting in the transit queue for an extended period.”

--With assistance from Ruth Liao.