The pair shared the sixth row of the grid and collided on the first lap when Hartley's Toro Rosso spun Perez's Force India around at Turn 4 during early battling.

Hartley received a 10s penalty for causing that incident and went on to finish a lapped 13th, while Perez finished 12th.

But the stewards summoned both drivers to a hearing after the race to discuss a separate incident that occurred between them before the race got underway.

Perez overtook Hartley on the formation lap, after Hartley was slow away from the grid, and did not allow Hartley to recover position, while Hartley failed to follow a procedure that dictates drivers who do not recover position before the first safety car line must start from the pitlane.

Under F1's sporting rules, drivers slow away on the formation lap can reclaim position provided they don't drop all the way to the back of the field.

After reviewing video evidence and hearing from Perez, Hartley and their respective teams, the stewards elected to add 30s to the race time of both drivers in lieu of a 10s stop/go penalty.

The stewards' official statements said: "Car 11 (Perez) overtook car 28 (Hartley) before Turn 1 and then during the remainder of the formation lap made no noticeable effort to allow car 28 to regain his position.

"The driver of car 11 also admitted the driver of car 28 was not unduly delayed when leaving the grid to start the formation lap.

"In this case the stewards decided to not award penalty points as the penalty is the

sufficient.

"Car 28 was overtaken by car 11 during the formation lap, failed to re-establish his position before the first safety car line and then did not enter the pits as required under Article 38.3."

Hartley was also handed two penalty points on his licence, taking his 12-month total to four.

The penalties dropped the drivers to 16th and 17th in the results.

Race director Charlie Whiting suggested after the race the incident was caused by Hartley being unsure of the correct procedure to follow.

"I haven't heard what Perez and Hartley have had to say yet, but Hartley didn't actually know what he had to do," Whiting said.

"On the one hand, yes, Perez did overtake, but that's fairly normal because not all cars leave the grid in the order of the grid.

"The rule is written primarily for cars last away from the grid, but he can make his way back through the field, as long as he's got back to his original position - like [Daniil] Kvyat in Canada last year.

"As long as he's done that, he can start from the grid. If not, he has to start from the pits. Hartley didn't [start from the pits], but he [also] didn't actually try and get back [into position]. This is the slightly odd thing."