SINGAPORE - Ahmad Danial Mohamed Rafa'ee, 35, was charged in court on Thursday (Dec 17) with the murder of Ms Felicia Teo Wei Ling on June 30, 2007.

Ms Teo was last seen by her parents on June 29, 2007, after leaving her home in Bras Basah. The 19-year-old was spotted later that evening entering a lift at Block 19 Marine Terrace with two men.

A missing persons police report was lodged by her mother on July 3 and Ms Teo's disappearance sparked a search involving more than 200 people.

After new leads were uncovered by the Criminal Investigation Department in July this year, Ahmad Danial was charged in court with the murder of Ms Teo. Police is looking for another man, Ragil Putra Setia Sukmarahjana, for helping Ahmad Danial.

The Straits Times looks at four other unsolved missing persons cases over the years.

1. Tina Lim Xinying

Missing since: June 22, 2002

Tina Lim Xinying was 14 years old when she went missing. The then Secondary 2 student left her Choa Chu Kang flat on June 22, 2002, to visit her cancer-stricken grandfather at his Jurong West home.

Tina had called her aunt, who lives with her grandparents, to tell her of her visit. Tina never arrived at her grandfather's home. Neither did she return home later that day.

Her father, Mr Lim Boon Kee, searched for her at her favourite spots, Lot One Shoppers' Mall and Jurong Point.

He spent more than $1,000 on advertisements in The New Paper, the Straits Times, Shin Min Daily News and Lianhe Wanbao asking for clues of his daughter's whereabouts.

Mr Lim also distributed more than 7,000 flyers and extended his search to Malaysia and Thailand.

On Nov 1, 2003, Mr Lim and six relatives received 10 calls they believed were from Tina. The police later investigated the calls and determined they were not from the girl.

2. Kouk Leong Jin

Missing since: Sept 27, 2011

Mr Kouk Leong Jin, a fourth-year medical student at Duke-NUS Medical School, arrived in Athens on Sept 25, 2011, for the 9th International Scientific Meeting of the Royal College of Obstetricians and Gynaecologists.

The 28-year-old sent his wife, Ms Seow Shu Ping, an e-mail a day later, on Sept 26. The following night - just after 10pm - he called his friend Neo Ghim Hoe, who was also in Greece for the conference. However, Mr Neo missed the call. When he returned the call the next morning, Mr Kuok did not answer his phone. No one heard from Mr Kouk again.

According to hotel records, Mr Kouk's last access to his room was on Sept 27 and he failed to turn up at the conference. A police report was lodged in Singapore by Ms Seow three days later.

Ms Seow, who had just married Mr Kouk three weeks earlier, flew to Greece with his parents and brother to look for him.

She also appeared on a 10-minute broadcast on Greek television on Oct 3, 2011, appealing for information regarding her husband.

3. Thomas Yeo See Ming

Missing since: March 15, 1994

Mr Thomas Yeo See Ming, 36, was last seen on Pulau Sibu Besar, an island off the east coast of Malaysia.

He left Singapore on Feb 28, 1994, to meditate on the island for a month, and was due to return at the end of March.

On March 3, he checked into a resort on the island, and was last seen 12 days later.

A week later, his family lodged a report with the Mersing police, who found that Mr Yeo's belongings, including money, passport and clothes were left in his hotel room.

Mr Yeo's mother, Madam Lee See Moi, went to the island in March 1994 to await the results of a search for her son.

In 2005, Mr Yeo's family appeared on a television programme about missing persons and revealed that every Chinese New Year, someone would call their house phone but hang up after a while without speaking.

4. Pham Thi Hai Yen

Missing since: Nov 13, 2012

Ms Pham Thi Hai Yen, 16, was supposed to return to Australia from Ho Chi Minh City, Vietnam, to continue her studies. Instead, the university student changed course and boarded a flight to Singapore with an unknown woman.

On Nov 12, 2012, Ms Pham travelled to the airport in Ho Chi Minh City with her family sending her off. That night, her family was informed by the airport that Ms Pham had left her luggage behind before boarding a plane bound for Singapore.

Her family tried to contact her but her phone was switched off. Her father was told by the Embassy of Vietnam in Singapore that she arrived in Singapore on Nov 13. There were no records of her leaving the country.

According to Ms Pham's father, she had spoken of recently befriending an unknown woman whom she met online. The woman had promised to fulfil her dreams of becoming a supermodel.