The latest Special Bulletin (PDF) for Tungurahua was issued by the Instituto Geofísico at 22:00 local time on 10 February 2008 (03:00 GMT 11 February 2008):

The volcanic activity of Tungurahua has from the evening of Sunday, 10 February once again shown a sharp increase, although on this occasion the increase is not in internal tremors or explosive activity, or the generation of pyroclastic flows, as happened between Wednesday and Friday. This time it is the constant emission of abundant ash, which is characteristic of an open volcanic conduit and the presence of dissolved gas in the magma impelling the eruption column several kilometers high into the atmosphere.

From approximately 15:00 today [10 February 2008] the volcano has considerably increased its emission of ash, which became very abundant after 16:45 and continues at the time of this report. The emission column is sustained, steady and very full of ash, rising to a height of 5 km above the crater. The prevailing wind direction is towards the south-west, towards the town of Riobamba, so the ash fall in that city is abundant, as it is in the districts of Guano, Colta and Penipe. It cannot be ruled out that the ash will even reach the city of Guaranda and surrounding districts. On the other hand, from 20:00 another current of wind is carrying more significant quantities of the ash from the eruption column in the direction of Puyo.

The authorities have already been advised by telephone at around 18:00. This new change in the type of volcanic activity at Tungurahua confirms its internal instability, but does not change the interpretation expressed in our previous report of 8 February regarding the likelihood of new large explosive eruptions. We consider that the probability of the latter, although it remains  a possibility, has in the short term declined. Rather, we believe that the eruption of abundant ash could continue to characterize the activity of the volcano in the coming days since the volcanic system is open.

The IG remains attentive to the changing condition of the volcano and will report developments immediately to the appropriate authorities.

Information
Smithsonian Institution Global Volcanism Program – summary information for Tungurahua (1502-80=)
Instituto Geofisico (Escuela Politecnica Nacional) – Geophysical Institute of Ecuador
Informe de actividad Volcán Tungurahua – special bulletins from the Instituto Geofísico