Archaeologists digging at the Alamo grounds are puzzling over the discovery of three separate earthen floors that may have been the site for an old granary at the historic mission.

 The floors also might mark the site of a building that was temporarily used as a church for several years when the first chapel collapsed in the1750s, according to dig supervisor Alton Briggs.

 "A few more pieces of the puzzle are here." Briggs said Friday. "Theymay not fit in yet, but they will."

 In any event, the building no longer existed at the time of the Alamobattle in 1836, he said.

 "The Alamo defenders never knew it had been there," Briggs said.

 The archaeological team from Austin was commissioned by the Alamo's caretaker, the Daughters of the Republic of Texas, to explore the areaaround the Alamo gift shop. The group plans to expand the basement storage and dig a tunnel to a proposed freight elevator next to Houston Street.

 Floors discovered are all on top of each other, with an estimated 15 to 20 years between each, Briggs said.

The first floor is roughly estimated to date to 1730, with the second layer 1750 and the final floor 1770, officials said.

There is no previous documentation depicting any building at the site, just to the west of the gift shop. All period maps of the mission show open areas where the building stood.

"But if you look atearly drawings, you see the chapel and then to the north of it, a large building," Briggs said, adding that perhaps the discovered floors belonged to that building.

 The dig team also has unearthed some flint arrowheads.