The Southern Kings may be in hot water with the South African Rugby Union, after they pushed the foreign envelope once too far.

It came on the day the Kings are heading for their first overseas trip - where they will play the Crusaders, Hurricanes, Brumbies and Rebels on consecutive weekends.

Super Rugby's rookies had three foreign imports - those not from the African continent - on the field in their 24-35 loss to the Chiefs last Friday.

That is one more that the SARU quote of two foreigners per 30-man Super Rugby squad and follows just a week after this website revealed how a widely-used custom and practice allowed the Kings to field four 'foreigners' against the Sharks.

SARU confirmed on Sunday that they have asked for an "explanation" as to why the Kings fielded an additional foreign player from outside the African continent.

"Media are advised that the selection of three overseas players by the Southern Kings in their match 22 against the Chiefs in Port Elizabeth on Friday [March 15] has been noted by SARU," a brief statement said.

"SARU will be contacting the Kings for a report on the situation."

The national body has consistently said the two-foreigners rule per team will remain in place and Friday was the first time the team from Port Elizabeth overstepped the mark.

The Kings had New Zealand import Hadleigh Parkes at inside centre in their starting XV, with Argentineans Tomàs Leonardi and Nicolas Vergallo on the bench.

Leonardi came for Wimpie van der Walt as a blood replacement in the 23rd minute and then for the injured Steven Sykes in  the 58th minute in PE on Friday.

Vergallo came on for Shaun Venter very late in the game, leaving the Kings with three foreigners on the field.

By Jan de Koning