Saudi Arabia opened an investigation.

Its air defenses did not stop a Houthi attack.

The attack was on Riyadh airport.

The strike killed at least 13 people.

It wounded more than 300 people.

Two regional officials said this on Monday.

The officials did not give their names.

They were not allowed to speak publicly.

The first probe showed something.

The Houthis first fired many drones.

The drones cleared the way.

Then cruise and ballistic missiles reached King Khalid International Airport.

Houthi ballistic missiles have warheads.

These warheads can change direction in flight.

This is hard for Saudi Patriot interceptors.

One official said the probe looks at something else.

Air defenses gave no early warning.

The missiles and drones flew over 1,000 kilometers (620 miles).

Then they reached Riyadh.

This attack is one of several Houthi strikes.

The Houthis have hit Saudi airports since last week.

It shows weaknesses in Saudi Arabia's defense system.

The Saudi-led coalition said something.

It intercepted and destroyed ballistic missiles two times.

These missiles were fired toward Riyadh on Monday.

People heard at least three explosions in the city.

This was Monday night.

Civil Defense officials later said the danger had passed.

The Saudis want the U.S. to take a more direct role.

They want the U.S. to fight the Houthis.

The U.S. has shared intelligence.

It has helped with target planning.

But it has not carried out strikes.

President Donald Trump said something on Saturday.

He was considering U.S. attacks on the Houthis.