Experts have taken a major step towards solving a 500-year-old murder mystery, confirming that two renowned literary figures from the 15th century were poisoned. After months studying the exhumed bodies of the two men, who died within a few months of each other in 1494, the committee overseeing the tests has confirmed the pair were probably killed by arsenic. High concentrations of the toxin was discovered in the bones of both the humanist philosopher Pico della Mirandola and the scholar and poet Angelo Ambrosini, better known as Poliziano.

The remains of the men, who were possibly lovers, were exhumed from their shared grave in a cloister of St Mark's Basilica in Florence last July.

Ever since his untimely death at the age of 31, there has been speculation that Pico was poisoned.

At the time it was rumoured that Poliziano, 40, was also poisoned although later scholars pointed to syphilis, of which there was a Europe-wide outbreak at the time. Both men were members of the powerful Florentine court of Lorenzo de' Medici.

After Lorenzo's death in 1492, Pico was increasingly drawn to the teachings of the book-burning Dominican friar, Girolamo Savonarola, and destroyed many copies of his own writing.

One popular theory was that Pico's own secretary poisoned him, angered at his friendship with the monk.

Silvano Vinceti, head of the national cultural committee that oversaw the exhumation, says there are a number of possibilities.

One theory is that the philosopher Marsilio Ficino, a close friend of both Pico and Poliziano, had a hand in their deaths.

Another option was the head of the inquisition at the time, a Spanish cardinal called Remolines, was responsible.

Vinceti gives credence to the involvement of Pico's secretary up to a point but believes the real culprit was someone else entirely: Lorenzo's son, Piero de' Medici.

''Combining the results of our analyses with historical documents that have only recently come to light it seems that Piero de Medici is the person most likely to have ordered the assassination,'' he explained. ''However, the person who actually carried out Pico's murder was probably Cristoforo da Calamaggiore, his secretary. In fact, he actually admitted to having poisoned him 'because he was sick'''.

Since their exhumation in July, the remains have been subjected to a battery of tests, using modern biomolecular technology, scanning equipment and DNA analyses. In addition to identifying the cause of death, the studies have also helped experts make conjectures about the men while they were alive. Pico's skeleton, for examples, suggests he was a robust man well over six feet tall - nothing like his portraits, which depict him as fairly slender. The studies have also shown that he suffered from a hammer toe and inflamed joints, which probably caused him stiffness. Another interesting discovery is that Pico, who was renowned for his prodigious memory, had an extremely large head. The tests suggest his cranial capacity was 1,768 cubic centimetres, compared to an average capacity of just 1,450 cubic centimetres. Poliziano was tiny in comparison to Pico - just five foot tall - and had a pronounced nose and problems with his neck. The studies also revealed that the men enjoyed a diet that was rich in protein but low in fish and carbohydrates. The remains of Poliziano, Pico, as well as the latter's friend, Girolamo Benivieni, who was buried with them later, were restored to their resting place in the cloister on Tuesday.

However, police DNA testing is continuing on bone samples, which may uncover further secrets about the men's life and death. A camera crew has closely followed the work of archaeologists and police involved in the project, and a documentary on the exhumation and investigation will be screened on Italian TV later this year.