Lava Tubes on Isla Ometepe

[MammothPaleoGuy]

I'm trying to put together the initial case for some research, and the literature thus far has let me down. I need to know about the conditions on Isla Ometepe in Lake Nicaragua. There are two composite-cone volcanoes there -- Concepcion and Maderas -- and I need to know if any of the basalt flows produce lava tube caves. Anybody know how I could find out? References, maps, or personal experience would be great!