NEW YORK (AP) – The tragic sinking of the Titanic nearly a century ago can be blamed on low grade rivets that the ship’s builders used on some parts of the ill-fated liner, two experts on metals conclude in a new book.

The company, Harland and Wolff of Belfast, Northern Ireland, needed to build the ship quickly and at reasonable cost, which may have compromised quality, said co-author Timothy Foecke. That the shipyard was building two other vessels at the same time added to the difficulty of getting the millions of rivets needed, he added.

“Under the pressure to get these ships up, they ramped up the riveters, found materials from additional suppliers, and some was not of quality,” said Foecke, a metallurgist at the U.S. government’s National Institute of Standards and Technology who has been studying the Titanic for a decade.