Lithuania's postal service unearthed hidden letters during a vault reconstruction, delivering some letters to their recipients half a century after they were sent.

One of the letters written to a 12-year old girl in Lithuania was delivered in December, almost 51 years after it was sent by a pen pal in Poland.

"I thought that someone was pranking me," said Genovefa Klonovska after being handed the letter, which included a handmade colored rose and two paper dolls.

The letter, together with 17 others, fell out of a ventilation hole this summer, dirty and crumbled, as a wall was demolished in a former post office on the outskirts of Vilnius.

"The workers suggested we throw the old letters away, but I called the post office instead," said Jurgis Vilutis, the owner of the building. "I'm so happy they got interested."

The letters, from the late 1960s and early 1970s, were likely hidden by an unscrupulous postal worker after he searched them for cash or valuables, Vilutis said.

Lithuania was part of the Soviet Union then, and the senders were emigrant relatives or pen pals from places such as Australia, Poland, or Russia.

Street names and their numbering have changed in Vilnius, and post office workers spent months looking for the right houses and talking to current tenants and neighbors, tracking down where the recipients moved to.

Only five recipients were found. In several cases children of deceased recipients were handed a lost letter.

"We felt a moral duty to do this," said Deimante Zebrauskaite, head of the customer experience department at Lithuania Post.

"One lady compared the experience to receiving a message from a bottle thrown into the sea. People were emotional. Some felt they saw a part of the daily life of their deceased parents," Zebrauskaite said.

In the letter to Klonovska, sent from Koczary in Poland and stamped in 1970, a girl named Ewa complained buses no longer reach her village, so she has to walk in minus 23 degrees Celsius (minus 9.4 degrees Fahrenheit) cold, and asks for pictures of actors.

Now in her 60s, Klonovska has no memory of Ewa. She probably wrote Ewa after finding her address advertising for pen-pals in a newspaper, and the relationship ceased after the letter got undelivered.

"So good that the letter was inconsequential. The loss was not life-changing," said Klonovska. "What if they delivered a lost letter from a suitor to his love, and their wedding never happened?"