The opening practice round of the Formula One event was halted just eight minutes into the session when racer Carlos Sainz broke down in his Ferrari after it struck the object at around 200mph on Las Vegas Boulevard.

Competitor Esteban Ocon also then smashed into the debris in his Alpine vehicle.

Ferrari described the damage to Sainz's car as "extensive", while Alpine said Ocon will require a new chassis.

There were no reports of any injuries.

Ferrari team principal Frederic Vasseur said: "He [Sainz] said [he] hit something on track, and he didn't know what it was. It is just unacceptable for F1."

The practice round was suspended, while the second session was delayed by two-and-a-half hours while staff rushed to carry out emergency repairs.

Second practice resumed at 2.30am local time (10.30am UK time).

A spokesperson for F1 governing body FIA said: "Following an inspection, a concrete frame around a manhole cover has failed.

"We now need to check all of the other manhole covers, which will take some time."

Viewers described the disruption as a "shambles" in posts on social media, with many also expressing fears for the safety of the drivers taking part in the event, which has cost organisers half a billion dollars to set up.

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Red Bull team principal Christian Horner told Sky Sports: "They are going to have to check all the manhole covers and weld them or do something because you can see the damage that it has done.

"It's a great shame for the fans but safety comes first. We have got to get this right and hopefully it won't take too long."

It is the first time in four decades that the city has hosted a Grand Prix, with F1 executives vowing the much-hyped event would be the "greatest show on Earth".

It kicked off with a glittering opening ceremony featuring music stars including John Legend.

But there have also been criticisms over whether the city is a suitable location to hold the event.

Triple world champion Max Verstappen is among those to have raised concerns about the track, which he described as "not exciting".

The racer also told reporters he believed the event was "99% show and 1% sport".

However, Mercedes team principal Toto Wolff offered an impassioned defence of the Las Vegas Grand Prix.

"That is not a black eye, this is nothing," he said. "They're going to seal the drain covers, and nobody's going to talk about that tomorrow morning anymore.

"It's completely ridiculous, completely ridiculous. FP1 [Free Practice One] - how can you even dare trying to talk bad about the event that sets the new standards, new standards to everything."

He added: "And then you're speaking about a drain cover that's been undone. That has happened before, that's nothing. It's FP1. Give credit to the people that have set up this Grand Prix, that have made this sport much bigger than it ever was."

It is not the first time that street fixtures have caused disruption to the sport.

Jenson Button struck a dislodged drain in practice in Monaco in 2016, while George Russell also ran over a drain cover in Azerbaijan four years ago.