PODGORICA, Montenegro -- Romania is sending planes to bring home survivors of a bus crash that killed 18 tourists in central Montenegro.

A military aircraft arrived in Montenegro's capital Podgorica on Monday, where 29 people have been hospitalized, including a Montenegrin child who was hurt at the site of the crash, officials said. Four remain in critical condition.

Another two medically equipped planes will be sent on Tuesday, and transport of the injured will depend on their condition, Romanian health ministry official Raed Arafat said.

The bus fell from a bridge over the Moraca river during a rainstorm and crashed some 40 meters (130 feet) into a ravine on Sunday.

It was not immediately clear what caused the driver to lose control but the winding road that leads from Serbia in the north through the Moraca canyon and then to the sea coast is notorious for traffic accidents because it is narrow, and slippery in wet weather.

Police initially said that 13 people were killed, but the number of fatalities grew to 18 overnight. Forensic pathologist Miodrag Soc told the AP that the victims will be identified by their families.

"Unfortunately, we lost 18 people and that is a huge tragedy for Romania," the health ministry official Arafat said, speaking in Podgorica.

Romanian President Traian Basescu and Prime Minister Victor Ponta sent their condolences to the victims. The country's Foreign Minister Titus Corlatean arrived in Montenegro where he met the president before heading to the hospital to meet survivors, the Romanian foreign ministry said. Ponta later said that the country would hold a day of national mourning on Wednesday for the victims.

Montenegrin police said they have started pulling the twisted wreckage of the bus out of the ravine.

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Alison Mutler contributed from Romania; Dusan Stojanovic and Jovana Gec from Serbia.

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  • People look at the scene of a bus accident near Grlo picture on June 23, 2013. Thirteen people died and 32 others were injured when a Romanian bus crashed in a Montenegro gorge on Sunday, Interior Minister Rasko Konjevic said. (SAVO PRELEVIC/AFP/Getty Images)

  • Emergency services attend the scene of a bus crash near Kolasin some 30 kilometers (18 miles) north of the capital Podgorica, Montenegro, Sunday, June 23, 2013. At least 13 people were killed and 32 were injured when a bus carrying Romanian tourists swayed off a bridge and plunged into a deep ravine in central Montenegro on Sunday, police said. The winding road that leads from Serbia in the north through the Moraca canyon and then to the seacoast is notorious for traffic accidents because it is narrow and slippery in wet weather conditions, and is considered one of the most dangerous to drive in the region. (AP Photo/Risto Bozovic)

  • Emergency services attend the scene of a bus crash near Kolasin some 30 kilometers (18 miles) north of the capital Podgorica, Montenegro, Sunday, June 23, 2013. (AP Photo/Risto Bozovic)

  • Police officers and rescuers carry the body of a victim after a bus crash near Kolasin some 30 kilometers (18 miles) north of the capital Podgorica, Montenegro, Sunday, June 23, 2013. (AP Photo/Risto Bozovic)

  • Emergency services attend the scene of a bus crash near Kolasin some 30 kilometers (18 miles) north of the capital Podgorica, Montenegro, Sunday, June 23, 2013. (AP Photo/Risto Bozovic)

  • Emergency services attend the scene of a bus crash near Kolasin some 30 kilometers (18 miles) north of the capital Podgorica, Montenegro, Sunday, June 23, 2013. (AP Photo/Risto Bozovic)

  • Emergency services attend the scene of a bus crash near Kolasin some 30 kilometers (18 miles) north of the capital Podgorica, Montenegro, Sunday, June 23, 2013. (AP Photo/Risto Bozovic)

  • Emergency services attend the scene of a bus crash near Kolasin some 30 kilometers (18 miles) north of the capital Podgorica, Montenegro, Sunday, June 23, 2013. (AP Photo/Risto Bozovic)

  • An injured woman is taken to an ambulance at the scene of a bus accident near Grlo on June 23, 2013. (SAVO PRELEVIC/AFP/Getty Images)

  • Montenegro's rescuers carry a dead passenger from the scene of a bus accident near Grlo on June 23, 2013. (SAVO PRELEVIC/AFP/Getty Images)

  • An injured man is taken to an ambulance at the scene of a bus accident near Grlo on June 23, 2013. (SAVO PRELEVIC/AFP/Getty Images)

  • An injured man is taken to an ambulance at the scene of a bus accident near Grlo on June 23, 2013. (SAVO PRELEVIC/AFP/Getty Images)

  • An injured man is taken to an ambulance at the scene of a bus accident near Grlo on June 23, 2013. (SAVO PRELEVIC/AFP/Getty Images)

  • An injured man is taken to an ambulance at the scene of a bus accident near Grlo on June 23, 2013. (SAVO PRELEVIC/AFP/Getty Images)

  • Rescuers work at the scene of a bus accident near Grlo on June 23, 2013. (SAVO PRELEVIC/AFP/Getty Images)